KR102356781B1 - Method for transmitting data in multi input multi output wireless communication system - Google Patents

Abstract

The present invention proposes a method in which a transmitter transmits a signal to a receiver in a multi-antenna-based wireless communication system. In particular, the method according to the present invention comprises the steps of: generating a bit stream of a specific bit size by channel-coding data; dividing the bit string into a first bit string having a first bit size and a second bit string having a second bit size; and allocating a second bit stream of the second bit size to an antenna sequence codeword based on a signal transmission time. and transmitting the first bit stream of the first bit size to the receiving end according to the order of the antenna pairs indicated by the allocated antenna sequence codeword.

Description

Method for transmitting data in a multi-antenna-based wireless communication system {METHOD FOR TRANSMITTING DATA IN MULTI INPUT MULTI OUTPUT WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a wireless communication system, and more particularly, to a method for transmitting data in a multi-antenna-based wireless communication system.

The present invention provides a better BER (Block Error) than a spatial modulation (SM) method for allocating a bit string to a transmit antenna index, a space time block code (STBC) and a space time block coded spatial modulation (STBC-SM) method in which the SM method is combined. Rate) to a wireless data transmission/reception method capable of providing performance. Prior to describing the present invention, the SM method and the STBC-SM method will be briefly described.

In addition, the present invention transforms the codeword matrix used in GBD-QOSTBC (Generalized block diagonal quasi-orthogonal space time block code) to define a sequence (consisting of an antenna index) that the terminal can distinguish into different information. As such, GBD-QOSTBC is also briefly described.

First, GBD-QOSTBC will be described.

The transmit antenna is M _T , create a GBD-QOSTBC codeword matrix of size M _T × M _T. First, M _T Alamouti codeword of = 2 is defined as a matrix A( s _i , s _{j ) as shown in Equation 1 below.} Symbols s _i , s _j is a complex symbol on the signal constellation ψ (ie, s _i , s _j ∈ψ).

Based on Equation 1, the QO-STBC code is expressed as an ABBA code as shown in Equation 2 below in an environment where M _{T = 4.}

In Equation 2, the diversity gain obtainable by using the ABBA code is still 2. Therefore, in order to obtain a diversity gain of 4 as much as the number of transmit antennas, phase rotation of symbols s ₃ and s _{4 is required.} A phase-rotated QO-STBC codeword matrix is defined as in Equation 3 below.

(단,

)이다. 특히, 수학식 3에서 나타낸 Q-OSTBC 행렬을 블록 대각 행렬 형태(GBD-QOSTBC)로 변형하기 위해서 신호 성상도 위의 심볼

에 대해서 홀수 및 짝수 인덱스에 해당되는 심볼을 구분해서 정의한다. 즉, 홀수 인덱스 심볼: s _odd = [s ₁ s ₃ … s _{2 k -1}] ^T 로 정의하고, 짝수 인덱스 심볼은 s _even = [s ₂ s ₄ … s _{2 k} ] ^T 로 정의한다.In Equations 2 and 3, s ₁ , s ₂ , s ₃ , s ₄ ∈ψ,

(only,

)to be. In particular, in order to transform the Q-OSTBC matrix shown in Equation 3 into a block diagonal matrix form (GBD-QOSTBC), the symbol on the signal constellation

For , the symbols corresponding to odd and even indices are distinguished and defined. That is, odd index symbols: s _odd = [ s ₁ s ₃ … s _{2 k -1} ] ^T , and an even index symbol is s _even = [ s ₂ s ₄ … s _{2 k} ] ^T is defined.

A new symbol is defined as in Equation 4 through the following linear operation of the above symbol.

In order to distinguish the signal constellation of the symbol newly defined in Equation 4, it is defined as Г. That is, the symbol of Equation 4 is defined as S _{j ∈Г.}

In Equation 4, all 2k symbols were classified into two sets with odd and even indexes. Here, the kxk matrix T is an arbitrary Hadamard matrix, and the phase rotation matrix D for obtaining the maximum diversity gain is expressed by Equation 5 below.

을 가정하면, 상기 수학식 3을 블록대각 행렬로 수학식 6과 같이 다시 정의할 수 있다.Hadamard matrix of Equation 4

Assuming , Equation 3 can be re-defined as Equation 6 as a block diagonal matrix.

)의 구조는 서로 다르지만, 평균적인 BER 성능은 동일하다.In Equations 4 and 6, symbols s ₁ and s ₂ are symbols on the original signal constellation ψ without phase rotation, and thus θ ₀ = 0 of the matrix D. In addition, the existing QO-STBC codeword matrix ( C ₄ ) of Equation 3 and the GBD-QOSTBC codeword matrix of Equation 6 (

) structure is different, but the average BER performance is the same.

As another example of GBD-QOSTBC, consider a codeword matrix C _{8 with} M _{T = 8.} For a total of 8 transmission symbols, two symbols are used as a pair as shown below, and symbols of different pairs belong to the signal constellation rotated to different phases as shown in Equation 7 below.

이다. M _T = 8 , QPSK 심볼을 전송하는 경우,

이다. 수학식 4의 임의의 하다마드 행렬 T 를 다음 수학식 8과 같이 가정한다.In this case, θ ₀ = 0 . The phase is determined according to the number of antennas and the modulation order of the transmission symbol. M _T = 8 , when transmitting a BPSK symbol,

to be. M _T = 8 , when transmitting QPSK symbols,

to be. It is assumed that an arbitrary Hadamard matrix T in Equation 4 is expressed in Equation 8 below.

Also, the codeword matrix C ₈ is expressed by Equation 9 below.

A matrix A( s _i , s _j ) is defined in Equation 1 above. For any r ≥ 2 , when M _T = 2 k = 2 ^r , the GBD-QOSTBC matrix can be generalized as in Equation 10 below.

In the codeword matrix of Equation 10, a horizontal axis indicates an antenna index, and a vertical axis indicates a time slot index. The number of transmit antennas is M _T = 2 k = 2 ^r In the case of M _T = 6 that cannot be expressed as , a codeword for M _T = 6 can be created by creating a GBD-QOSTBC codeword matrix for M _T = 8 and deleting the last two rows and columns.

Next, the SM technique will be described.

The SM technique is a method of allocating binary data to each transmit antenna index, selecting an antenna corresponding to a bit string to be transmitted, and transmitting a data stream. That is, the total amount of information to be transmitted is the sum of the amount of information allocated to the data stream and the amount of information allocated to the antenna index.

1 is a conceptual diagram of an SM technique. Referring to FIG. 1 , it can be seen that the total amount of information to be transmitted is the sum of the amount of information possessed by a transmission symbol and the amount of information allocated to an antenna index used to transmit the same.

More specifically , when there are M _T transmit antennas, a maximum of log ₂ M _T bits may be allocated to the transmit antenna index. Assuming a PSK or QAM symbol with a modulation order of M , the total amount of information (m) that can be transmitted by the SM technique (expressed in bits per channel use) is m = log ₂ ( M _T ) + log ₂ ( M ) can be defined as

For example, when transmitting 3 bits per channel use, when there are 2 transmit antennas and a modulation order is 4, and when there are 4 transmit antennas and a modulation order is 2, the SM technique can be applied as shown in Table 1 below. In Table 1 below, M _T = N _t , antenna number is an antenna index, and transmit symbol is M-PSK, M-QAM symbol.

Finally, the STBC-SM technique will be described.

Total transmit antenna M _T Among them, L × L STBC codewords are assumed using L. Above SM scheme it should be used to continue the L antenna, while when transferring data with STBC-SM scheme selected for the STBC code word length L time slots to assign a bit sequence for each antenna index.

이다. 따라서 송신 심볼과 (M-PSK 또는 M-QAM) 안테나 인덱스에 실어서 전송하는 총 정보량(m)은

로 정의될 수 있다.The amount of information (expressed in bits per channel use) that can be sent on the antenna index is

to be. Therefore, the total amount of information (m) transmitted in the transmission symbol and (M-PSK or M-QAM) antenna index is

can be defined as

, M = 2(BPSK) 인 경우를 가정하여 예시한다. M _T = 4, L = 2,

, M = 2 ( BPSK ) is exemplified.

Two of the four transmit antennas are selected and data is transmitted using the Alamouti technique for two time slots. Two of the transmit antenna indices 1 to 4 are selected and 2 bits are allocated as shown in Table 2 below. The STBC-SM codeword corresponding to the selected antenna is shown in Equation 11 below. In Equation 11, the vertical axis indicates the antenna index, and the horizontal axis indicates the time slot index.

It can be seen from Equation 11 that the codeword elements of the codebook X ₂ all rotate by θ , which serves to improve the BER performance by maximizing the distance between symbols defined in the two codebooks. The value of θ varies depending on the number of transmit antennas and modulation order, and since it cannot be found in a closed form, it must be found experimentally. It will be described below with reference to the drawings.

2 is a conceptual diagram of the STBC-SM technique. In FIG. 2 , it is assumed that θ = π /2 for convenience of explanation.

x ₁ and x ₂ are BPSK symbols transmitted by each antenna. Accordingly, since a total of 2 bits are transmitted by 1 bit for each antenna during two time slots, and 2 bits are additionally transmitted as an antenna index, a total of 4 bits are transmitted. Here, the 4-bit string is represented by u ₁ , u ₂ , u ₃ , and u ₄ as shown in FIG. 2 . Among them, assuming that u ₁ , u ₂ are bit streams allocated to antenna indexes, and u ₃ , u ₄ are allocated to BPSK symbols and transmitted as bit strings, it can be represented by a block diagram as shown in FIG. 2 .

On the other hand, the channel does not change only during the L < M _T time slot, the transmit antenna M _T Of the you to select L pieces assumed to transmit data at a fixed rate, since STBC-SM technique is to transfer some of the aggregate transmit data to the SM technique, using the STBC code words of the existing L × L size data It is possible to reduce the amount of information to be transmitted in a transmission symbol rather than to transmit, and thus a BER gain can be obtained.

Based on the above discussion, a method for transmitting data in a multi-antenna-based wireless communication system is proposed below. In particular, the present invention proposes an effective wireless data transmission/reception technique in an open loop multiple input multiple output (MIMO) system.

A method for a transmitting end to transmit a signal to a receiving end in a multi-antenna-based wireless communication system according to an embodiment of the present invention comprises: generating a bit stream of a specific bit size by channel-coding data; dividing the bit string into a first bit string having a first bit size and a second bit string having a second bit size; allocating a second bit stream of the second bit size to an antenna sequence codeword based on a signal transmission time; and transmitting the first bit stream of the first bit size to the receiving end according to the order of the antenna pairs indicated by the allocated antenna sequence codeword.

Here, the antenna sequence codeword is characterized in that it is defined by two time slots and two antenna indices.

Specifically, the step of transmitting the first bit string of the first bit size includes: in units of time slots, according to the order of the antenna pairs indicated by the allocated antenna sequence codeword, the first bit string of the first bit size It is characterized in that it comprises the step of transmitting the QO (quasi-orthogonal)-STBC (space time block code) technique. Here, the allocated antenna sequence codeword is characterized in that it indicates an antenna pair through which data is transmitted in two time slots.

Preferably, the sum of the first bit size and the second bit size is the specific bit size.

According to an embodiment of the present invention, data can be transmitted more effectively in a multi-antenna-based wireless communication system.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description. will be.

1 is a conceptual diagram of an SM technique.
2 is a conceptual diagram of the STBC-SM technique.
3 illustrates an example of generating an antenna index sequence according to an embodiment of the present invention.
4 is a diagram illustrating a relationship between the number of antennas and a maximum amount of information when an antenna index sequence is used according to an embodiment of the present invention.
5 shows the structure of a transmitter according to an embodiment of the present invention.
6 shows the structure of a receiver according to an embodiment of the present invention.
7 is a diagram illustrating another structure of a receiver according to an embodiment of the present invention.

In order to increase the frequency efficiency per cell, since the amount of information per transmission symbol must be high, symbol transmission with a high modulation level is required. However, when a symbol with a high modulation level is transmitted, the minimum distance between symbols on the signal constellation naturally decreases, so that the BER performance at the same SNR is deteriorated. In a closed-loop MIMO system in which the base station can utilize channel information between transceivers, the effective reception SNR can be increased by using the MIMO beamforming technique, thereby directly increasing the Achievable Rate.

However, in the open-loop MIMO system, since the receive SNR gain is determined by the number of receiver antennas, it is difficult to directly improve the data rate unless the transmit power is amplified even if the base station has many antennas. Accordingly, an object of the present invention is not to improve the data rate by increasing the received SNR, but to improve BER performance compared to existing open-loop MIMO data transmission/reception schemes when the same amount of data is transmitted in an open-loop MIMO system.

The present invention is mainly characterized by transforming the GBD-QOSTBC codeword matrix only within the constraint that maintains the diversity gain in terms of the BER performance of the QO-STBC technique. Modification of the codeword is the same as changing the antenna used according to the data transmission time, and based on this, a sequence composed of the transmit antenna index is defined and used to transmit data. Ultimately, the total data to be transmitted is divided into a transmission symbol and an antenna index sequence and transmitted. The present invention refers to this data transmission scheme as STBC-SSC (space time block coded spatial sequence coding). First, the codebook used in the present invention will be described.

A) Codebook Definition

(1) X _{QAM, QOSTBC} : QO-STBC symbol vector codebook (composed of M-PSK and M-QAM symbols)

을 아래 수학식 12를 살펴본다.It is a codebook used to create an M _T × M _T codeword matrix of the existing QO-STBC technique. In the proposed method, it is used when converting to GBD-QOSTBC symbol. QO-STBC codeword is 2x2 Alamouti codeword (Orthogonal STBC) M _T = 2 ² ,2 ³ ,...,2 ^r is extended to an M _T × M _T matrix based on the ABBA codeword. Accordingly, the QO-STBC codeword matrix has a half-orthogonal feature. That is, each row vector (or column vector) constituting the QO-STBC codeword matrix is perpendicular to different M _T /2 row vectors (column vectors). In order to easily understand these characteristics, using the QO-STBC codeword of Equation 3 above,

Look at Equation 12 below.

이고,

이다. 또한, 수학식 12에서 joint-ML 디코딩이 필요한 심볼의 쌍이 (s ₁,s₃),(s ₂,s₄) 임을 알 수 있다. 임의의 M _T 에 대해서 확장하면, M _T /2 개의 심볼로 구성된 두 쌍에 대해서 각각 joint-ML 디코딩이 필요함을 알 수 있다.in Equation 12

ego,

to be. In addition, it can be seen from Equation 12 that the pair of symbols that require joint-ML decoding are ( s ₁ ,s ₃ ), ( s ₂ ,s _{4 ).} any M _T Expanding to , it can be seen that joint-ML decoding is required for two pairs of M _{T /2 symbols, respectively.}

개의 벡터로 아래 수학식 13으로 정의한다.As a result, the X _QAM,QOSTBC codebook is composed of a codeword vector of size M _{T /2×1.} The elements of the vector are symbols such as M-PSK, M-QAM, and total

It is defined by Equation 13 below as a vector of .

,n∈{1,2,...,M _T /2} 이다.In Equation 13, s _n [ k ]∈ψ, in this case

, n ∈{1,2,..., M _T /2} .

(2) X _G-STBC : GBD-QOSTBC symbol vector codebook

Using Equation 4 above, codeword vectors of X _{QAM and QOSTBC} defined as QAM or PSK symbols are converted into GBD-QOSTBC symbols as shown in Equation 14 below.

Equation 14 can be simply understood as 1:1 mapping between codeword vectors as shown in Equation 15 below.

Referring to Equations 14 and 15, since the vector is mapped in units of vectors, the codeword vector of X _G-STBC closest to the received signal vector is determined, and then a symbol vector composed of QAM symbols of X _{QAM and QOSTBC is obtained through inverse operation.} look for The symbols used in Equation 14 are summarized as follows.

- S[ k ]: Codeword vector of size M _T /2×1:

- S _j [ k ]: elements of vector S[ k ], j ∈{1,2,... M _T /2}

- S _j [ k ]∈Г

(3) X _Ant : Antenna Index Sequence Codebook

Two consecutive time slots are expressed in one unit as t = (1,2), (3,4),..., ( M _T -1, M _T ), and the antenna index to be used according to the transmission time is determined. define. That is, two antenna indexes to be used in two consecutive time slots are defined. Two antennas become one symbol constituting an antenna index sequence as a pair. Accordingly, M _T /2 antenna pairs constitute one sequence, and a set of different antenna index sequences is X _Ant . Antenna sequence codebook X _Ant is expressed as in Equation 16 below.

Here, B _SSC is an amount of information allocated to an antenna index sequence and transmitted, and its unit is a bit. Also, I _j is the j-th antenna index sequence, u _j is I _j A bit sequence corresponding to . Specifically, I _j and u _j can be expressed as in Equation 17 below.

(4) X _H : set of effective channel matrices

X _H is a set of effective channel matrices of size M _T × M _T corresponding to the antenna index sequence defined in the codebook X _Ant. This information is possessed only by the UE in the open-loop MIMO system, and is expressed by Equation 18 below.

는 X _Ant 의 I _j 에 따라서 결정된다. j번째 안테나 시퀀스를 사용해서 데이터를 전송하고, 두 타임 슬롯 (t ₀, t ₀+1) 에서 사용하는 송신 안테나 쌍을 (m ₁,m ₂) 라고 가정하면, 이에 상응하는 유효채널

의 4개 원소를 아래와 같이 구성한다. B _SSC in Equation 18 is the amount of information allocated to the antenna index sequence in the same way as above. procession

is X _Ant of I _j is determined according to Assuming that data is transmitted using the j-th antenna sequence, and a transmission antenna pair used in two time slots ( t ₀ , t ₀ +1) is ( m ₁ , m ₂ ), a corresponding effective channel

The four elements of is composed as follows.

이고, h(m ₂) 은 벡터 h 의 m ₂ 번째 원소로서, 윗 첨자 '*'는 켤레 복소수를 의미한다. 각 원소는 독립적이고 동일한 분산 가우시안 요소(independent and identically distributed Gaussian element)이고, 서로 다른 벡터 채널은 독립임을 가정한다.here,

, and h( m ₂ ) is the m _2nd element of the vector h, and the superscript '*' means a complex conjugate number. It is assumed that each element is an independent and identically distributed Gaussian element, and that the different vector channels are independent.

을 아래 수학식 19와 같이 구성한다.For example, the antenna indexes sequentially used in time slots (1,2), (3,4), (5,6), (7,8) are (1,3), (2,4), ( 5,7), if (6,8), matrix

is configured as in Equation 19 below.

B) Antenna index sequence generation

In the present invention, the GBD-QOSTBC codeword matrix in the form of a block diagonal matrix is transformed while maintaining the maximum space-time diversity gain provided by the GBD-QOSTBC technique. It will be described with reference to the drawings.

3 illustrates an example of generating an antenna index sequence according to an embodiment of the present invention.

로 표현한다.Two antennas used for two consecutive time slots become one symbol constituting a sequence, and as shown in FIG. 3 , the GBD-QOSTBC codeword matrix is transformed using a column vector as a unit. In FIG. 3, the GBD-QOSTBC codeword matrix on the left is C _{2 k} and the modified GBD-QOSTBC codeword matrix on the right

expressed as

는 블록대각 행렬 형태는 아니지만, 여전히

행렬은 대각 행렬이다. 또한,

와

은 동일한 대각 행렬이 아니고, 이에 상응하는 유효 채널 행렬도 동일한 원리가 적용된다. 따라서 단말은 서로 다른 정보로써 구분이 가능하다.here,

is not in the form of a block diagonal matrix, but still

The matrix is a diagonal matrix. Also,

Wow

is not the same diagonal matrix, and the same principle applies to the corresponding effective channel matrix. Therefore, the terminals can be distinguished by different information.

The maximum number of sequences that can be generated by transforming the M _T × M _T GBD-QOSTBC matrix in this way is the number of cases in which two M _T /2 times are selected without allowing overlap among the total M _{T transmit antennas.} , as in Equation 20 below.

In this way, the maximum amount of information that can be allocated to the antenna sequence index is expressed in Equation 21 below.

In Equation 12, when M _T is very large, ( α )→0, ( β ) is a constant value and is always less than 2. Therefore, when there are very many transmit antennas, B _SSC can be expressed as in Equation 21 above. Also, in the graph of FIG. 4 , it can be seen that the maximum amount of information increases in proportion to the log function as shown in Equation 21 as the number of antennas increases.

C) STBC-SSC signal transmission/reception procedure according to the present invention (STBC-SSC)

First, it is assumed that both the transceivers have the codebooks of (1) to (3) described above, and the receiver additionally has the codebooks of (4) through channel estimation.

5 shows the structure of a transmitter according to an embodiment of the present invention.

Referring to FIG. 5, first, an encoded bit stream (ie, codeword) is generated through channel coding for data to be transmitted. For convenience of explanation, a single codeword is assumed, and the total number of bits is N = B _QOSTBC + B _SSC assume Here, among the total N bits, B _QOSTBC bits are transmitted using the QO-STBC technique, and B _SSC bits are allocated to the antenna sequence and transmitted. The criterion for dividing the encoded bit stream of length N into two parts must be known to both the transceiver and the transceiver for the encoding and decoding processes.

개의 비트 열은 총

개의 안테나 시퀀스에 할당된다. 각 안테나 시퀀스에 할당된 비트 열에 대한 정보는 코드북 X _Ant 에 정의 되어있다. 또한, 아래 수학식 22와 같이 데이터 전송 시점에 따라서 전송하고자 하는 비트 열이 몇 번째 안테나 인덱스 시퀀스를 사용할 것인지 결정된다.of length B _SSC

The number of bit strings is

is assigned to an antenna sequence. Information on the bit string allocated to each antenna sequence is defined in the codebook X _Ant. In addition, as shown in Equation 22 below, it is determined which antenna index sequence is to be used for the bit stream to be transmitted according to the data transmission time.

을 전송한다.When the antenna index sequence codeword is determined, the order of the antenna pairs to be used in ( t ₁ , t ₂ )=(1,2),...,( M _T -1, M _{T ) is determined in the time slot pair.} GBD-QOSTBC symbols according to the determined order

to send

는 M _T 타임 슬롯 동안 받은 수신신호 벡터를 의미한다.Next, a receiver operation for recovering transmitted data will be described. 6 shows the structure of a receiver according to an embodiment of the present invention. vector in fig.

It refers to a received signal vector received during the time slot _T M.

Referring to FIG. 6 , the receiver finds codeword indexes of codebooks X _{QAM, QOSTBC} , X _G-STBC , X _H , and X _{Ant through decoding.} The overall decoding order is as follows. In FIG. 6, the joint ML (maximum likelihood) method for finding both the antenna sequence X _Ant and the X _{G-STBC symbol is shown.} A _{method of finding an X Ant} symbol will be described first, and a method of finding an X _{G-STBC symbol will be described later.}

(a) Joint-ML Decoding

에서 정의된 유효 채널 행렬 가운데, j 번째 행렬의 켤레 전치 행렬을 수신 신호 벡터에 곱하면 다음 수학식 23과 같다.The receiver performs Joint-ML decoding using the GBD-QOSTBC codebook ( X _G-STBC ) and the effective channel codebook ( X _{H) in which the antenna index sequence is reflected.} codebook

Among the effective channel matrices defined in , when the received signal vector is multiplied by the conjugate transpose matrix of the j-th matrix, the following Equation 23 is obtained.

의 홀수 및 짝수 인덱스에 해당되는 원소들을 구분하여 두 개의 벡터

로 구분한다.

는 다음 수학식 24과 같이 정의된다.Vector of Equation 23

Separate the elements corresponding to odd and even indices of

separated by

is defined as in Equation 24 below.

에 대해서 코드북 X _G-STBC 의 k번째 코드워드 벡터와 l ₂-norm 값을 아래 수학식 25 및 수학식 26과 같이 계산한다.Next, assuming that data is transmitted according to the j-th antenna index sequence, the GBD-QOSTBC codeword vector closest to the received signal vector is found in X _G-STBC. In this case, a distance measure for finding the nearest codeword vector is assumed to be l ₂ -norm, but other measuring methods are also possible. two symbol vector

For , the k-th codeword vector and l ₂ -norm value of the codebook X _G-STBC are calculated as shown in Equations 25 and 26 below.

In Equations 25 and 26, S[ k ]∈ X _G-STBC , a _j , b _j , c _j , d _j is derived from Equation 27 below.

)를 고려해서 수학식 25 및 수학식 26을 계산한다. 다음으로, X _H 의 모든 코드워드 행렬에 대해서 (

) 앞서 설명한 과정을 반복 수행함으로써 모든 k, j에 대해서

,

값을 찾는다. 이후, 계산한 값을 바탕으로 아래에 제시된 기준에 따라서 안테나 시퀀스 인덱스와 GBD-QOSTBC 코드워드 인덱스를 아래 수학식 28과 같이 결정한다.In addition, for the j-th codeword matrix of X _H , all codeword vectors of X _{G-STBC (}

) to calculate Equations 25 and 26. Next, for all codeword matrices of X _{H (}

) for all k and j by repeating the process described above.

,

find the value Thereafter, based on the calculated values, the antenna sequence index and the GBD-QOSTBC codeword index are determined as shown in Equation 28 below according to the criteria presented below.

In Equation 28, k ^* is a codeword vector index of the codebook X _G-STBC , and j ^* is a codeword matrix index of the codebook X _Ant.

(b) Through the inverse operation of Equation 14, X _QAM,QOSTBC symbol vectors are found as shown in Equation 29 below.

(c) Binary data is extracted through determination of transmission symbols such as QAM/PSK and demodulation of the determined symbols.

(d) A bit string allocated to the determined j ^* th antenna sequence is extracted from the codebook X _Ant.

(e) Combining the binary data extracted in (c) and (d) into one bit stream to compose the coded bit stream expected to be transmitted, and then decodes it and restores the original signal (binary data).

Hereinafter, an example of signal transmission in the STBC-SSC method of the present invention will be described based on the above description. First, it is assumed that 8 bits (that is, each 1 bit is transmitted through 8 antennas) are transmitted in the QO-STBC method, and 2 bits of data are additionally transmitted using SSC. Therefore, it can be defined as follows.

- 8x8 GBD-QOSTBC, M _T = 8

- B _STBC = 8 bits and B _SSC = 2 bits

- Constellation : BPSK (M=2)

In addition, depending on the system environment, internal parameters T and D are defined as follows.

,-

,

,

이다.- For 8 antennas and BPSK, the phase required to obtain the maximum space-time diversity of GBD-QOSTBC is θ ₀ = 0 ,

,

to be.

로 가정한다.- Hadamard procession

assume that

개의 4x1 코드워드 벡터를 원소로 갖는다. X _QAM,QOSTBC , X _G-STBC 은 아래와 같다.In order to transmit a total of 8 bits, each 1 bit per transmission data stream, one BPSK symbol for each M _T = Transmit during 8 time slots. The elements of the codebook X _{QAM, QOSTBC} and X _G-STBC are 4x1 vectors, and each element in one vector is determined by one of two BPSK signals. So X _QAM,QOSTBC , X _G-STBC is the total

It has 4x1 codeword vectors as elements. X _{QAM, QOSTBC} , X _G-STBC are as follows.

- X _QAM,QOSTBC = {s[1],s[2],...,s[16]} , s _n [ k ]∈{-1,+1}

- Parameter range: k ∈{1,2,...,16}, n ∈{1,2,...4}

- X _G-STBC = TD × X _QAM,QOSTBC = {S[1],S[2],...,S[16]}

The information transmitted to the transmit antenna index sequence is 2 bits in total, and the transmit antenna index sequence and the corresponding binary signal are defined as follows.

- X _Ant = { I ₁ , I ₂ , I ₃ , I ₄ ,u ₁ ,u ₂ ,u ₃ ,u ₄ }

I ₁ = (1,2), (3,4), (5,6), (7,8), I ₂ = (1,3), (2,4), (5,7), (6 ,8)

- I ₃ = (1,4), (2,5), (3,8), (6,7), I ₄ = (1,5), (2,6), (3,7), ( 4,8)

- u ₁ = [0,0], u ₂ = [0,1], u ₃ = [1,0], u ₄ = [1,1]

은 다음과 같다.Next, the effective channel matrix codebook corresponding to X _Ant = { I ₁ , I ₂ , I ₃ , I ₄ ,u ₁ ,u ₂ ,u ₃ ,u _{4 }}

Is as follows.

If it is assumed that an arbitrary k-th symbol vector S[ k ]∈ X _G-STBC is transmitted using the sequence I ₂ and reception noise is omitted, Equation 23 is expressed as Equation 30 below.

에서

는 아래 수학식 31과 같은 형태를 갖는다.Especially,

at

has the form as in Equation 31 below.

,

,

,

와 같다.

, j = 1,3,4 경우에도 동일한 방식으로 유도된다. Based on this, parameters a ₂ , b ₂ , c ₂ , d ₂ corresponding to j = 2 in Equations 25 and 26 are

,

,

,

same as

, j = 1,3,4 is derived in the same way.

와 다른 시퀀스에 해당되는 채널행렬의 전치 행렬과의 곱

,

,

행렬은 대각행렬이 되지 않는다. 수신신호에 코드북 X _H 의 j번째 원소의 전치행렬을 곱한

의 홀수 및 짝수 원소들을 구분해서 복호화 하더라도, 잡음이 없는 경우, 항상 원하는 송신 심볼 벡터 및 사용한 시퀀스에 해당되는 유효채널 행렬을 찾아낼 수 있다. 따라서,

를 아래 수학식 32와 같이

,

로 분리해서 복호화한다.Effective channel corresponding to sequence I ₂

multiplied by the transpose matrix of the channel matrix corresponding to another sequence

,

,

The matrix is not diagonal. Codebook X _H in the received signal multiplied by the transpose matrix of the j-th element of

Even when the odd and even elements are separately decoded, if there is no noise, an effective channel matrix corresponding to a desired transmission symbol vector and a used sequence can always be found. thus,

as Equation 32 below

,

is separated and decoded.

,

값을 찾고, 아래 수학식 33을 통하여 송신 심볼 벡터 및 송신 안테나 인덱스 시퀀스를 결정한다.As shown in Equations 25 to 27

,

A value is found, and a transmit symbol vector and a transmit antenna index sequence are determined through Equation 33 below.

Hereinafter, a receiver structure having a lower computational complexity than that of the receiver of FIG. 6 is proposed.

7 is a diagram illustrating another structure of a receiver according to an embodiment of the present invention.

Since the receiver shown in FIG. 6 searches all QO-STBC symbols and all antenna index sequences together, complexity may increase excessively when there are very many antennas and when a modulation order is high. For this reason, a low-complexity reception technique for sequentially finding two antenna indices may be considered.

이 블록대각 행렬의 형태가 아니더라도

은 대각행렬이다. 이를 이용해서 두 개의 타임 슬롯을 기준으로 하나의 안테나 인덱스 쌍을 결정한다. 도 7에서 심볼 수신 시점에 따라서 수신 심볼 벡터를 아래 수학식 34와 같이 나타낸다.As can be seen in Equation 25, Equation 26 and Equation 31, the effective channel matrix

Even if it is not in the form of this block diagonal matrix

is a diagonal matrix. Using this, one antenna index pair is determined based on two time slots. In FIG. 7, a received symbol vector is expressed as Equation 34 below according to a symbol reception time.

First, the codebook X _G-STBC is used to find antenna index pairs. The QAM symbol defined in the codebook X _QAM,QOSTBC of Equation 13 is found by multiplying the inverse of the matrix TD of Equation 14 after decoding M _T /2 GBD-QOSTBC symbols. Therefore, even in the reception method of the present invention, after determining the antenna index sequence based on X _G-STBC , X _{QAM and QOSTBC} can be found. For convenience of description, four antenna index sequences in Equation 35 below are considered.

와 같고, 간섭 영향이 없는 경우 GBD-QOSTBC 심볼을 항상 찾을 수 있다.In the above, antenna index pairs that can be used at t = 1,2 are limited to (1,2), (1,3), (1,4), and (1,5). Therefore, only these four combinations are considered at t = 1,2. The same is true for t = 3,4 and subsequent time slots. If the k-th symbol vector of X _G-STBC is transmitted at t = 1,2 and the antenna index (1,3) is selected, two GBD-QOSTBC symbols are each

, and if there is no interference effect, the GBD-QOSTBC symbol can always be found.

As can be seen in equation 14, t = 1,2 in the S ₁ [k] and S ₂ [k], only to consider for S _j [k], _j ≥3 at t = 1,2, because it can transmit does not In the same principle in t = 3,4, it is only necessary to consider S _j [ k ], j = 3,4 in the X _{G-STBC codebook.} As a result, the GBD-QOSTBC symbol and the antenna index are searched together, but the computational complexity is lower than the joint-ML method presented above because it is not searched for the entire sequence, but based on two Alamouti blocks.

In summary, the present invention modifies the existing GBD-QOSTBC structure to create a sequence composed of a transmit antenna index, and allocates a binary data sequence to the created antenna sequence to transmit symbols (i.e., modulation symbols such as QAM and PSK). Part of the data to be loaded and transmitted is allocated to the antenna sequence. Accordingly, it is possible to prevent the minimum distance between symbols from being reduced as the modulation order increases, and to provide improved BER performance compared to GBD-QOSTBC in the SNR region above a certain level.

The existing STBC-SM method has to suffer diversity performance loss instead of obtaining an SM gain when transmitting a data stream. A similar gain to SM-MIMO is obtained by loading data into the .

Claims (5)

A method for a transmitting end to transmit a signal to a receiving end in a multi-antenna-based wireless communication system, comprising:
generating a bit stream of a specific bit size by channel-coding data;
dividing the bit string into a first bit string having a first bit size and a second bit string having a second bit size;
allocating a second bit string of the second bit size to a selected antenna sequence codeword from among a plurality of antenna sequence codewords based on a signal transmission time; and
Transmitting a first bit stream of the first bit size to the receiving end based on a plurality of antenna port pairs according to the order of the antenna pairs indicated by the assigned antenna sequence codeword,
The antenna sequence codeword includes indices of the plurality of antenna port pairs that do not overlap each other, and each of the plurality of antenna port pairs represents one bit of the second bit string,
How to transmit a signal. The method of claim 1,
The antenna sequence codeword is
characterized in that it is defined by two time slots and two antenna indices,
How to transmit a signal. The method of claim 1,
Transmitting the first bit stream of the first bit size comprises:
In units of time slots, according to the order of the antenna pairs indicated by the allocated antenna sequence codeword, the first bit stream of the first bit size is transmitted using a quasi-orthogonal (QO)-space time block code (STBC) technique. characterized in that it comprises the step of
How to transmit a signal. 4. The method of claim 3,
The allocated antenna sequence codeword is,
Characterized in indicating an antenna pair through which data is transmitted in two time slots,
How to transmit a signal. The method of claim 1,
The sum of the first bit size and the second bit size is the specific bit size,
How to transmit a signal.

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